Hyper-threading and the Sun Fire[TM] V60x and V65x

Asset ID:	1-71-1003411.1
Update Date:	2012-07-30
Keywords:

Solution Type Technical Instruction Sure

Solution 1003411.1 : Hyper-threading and the Sun Fire[TM] V60x and V65x

Applies to:

Sun Fire V60x Server - Version Not Applicable and later
Sun Fire V65x Server - Version Not Applicable and later
All Platforms
***Checked for relevance on 14-May-2012***

Goal

Allow customers to best choose the Hyper-Threading configuration for their operating environment and applications.

Fix

Enter the Main Content

Description

Hyper-threading is a recent technology that Intel has incorporated into the latest ATOM, Pentium 4, Core i and Xeon Server CPUs. Hyper-threading allows the scheduler to hand a CPU 2 separate program instructions simultaneously.

Hyper-Threading, sometimes also referred to as simultaneous multithreading (SMT), allows different threads to run simultaneously on different execution units within one physical processor.

Hyper-threading is not the same as having a multi-core CPU. Multi-core CPUs are many true CPUs mounted in the same casing, allowing much higher CPU densities. Both Sun and Intel have other CPU products with multi-core support.

Hyper-threading is an enhancement to the scheduler that allows the CPU to pretend to be multiple CPUs to optimize how instructions are processed.

This technology has its roots in development done by engineers who were working on incorporating it into future versions of the Alpha processor.

Steps to Follow
How do the Sun Fire V60x and V65x implement Hyper-threading.

Sun legacy Intel x86-based servers, the Sun Fire V60x and V65x, use Intel Xeon processors that are Hyper-threading capable. However Hyper-threading is not enabled by default.

Should the customer wish to enable Hyper-threading, the process to do so is simple:

Press <F2> while booting during the power-on self test (POST) to enter the BIOS configuration menu
Using the <Down> arrow key, scroll to Processor Settings then press the enter key
Toggle the feature Hyper-threading(tm)using the enter and arrow keys
Press the <Esc> key once to exit the Processor Settings menu
Press the <Left> arrow key to highlight the Exit menu
Press the <Enter> key to select Exit Saving Changes
Press the <Enter> key again to confirm the new BIOS setting
The system will continue booting with the new setting

When can Hyper-threading improve application performance

Hyper-threading improves performance primarily for single applications that are multi-threaded or systems that run multiple services. The improvement is quoted as being anywhere between 30% and 90% for heavily threaded applications, especially if they have been optimized to run on a Hyper-threading enabled CPU.

In some cases it may be more beneficial to have Hyper-threading disabled as most x86 applications today are typically not threaded or hyper-threading optimized. This is usually done through turning off Hyper-threading in the BIOS (this is done by default on the Sun Fire V60x and V65x). A couple of examples where this may be desirable:

For single-threaded dedicated function systems (most EDA, HPTC, rendering applications)

In systems that are optimized to run a single thread or process, like is often the case in High Performance Computing (HPC) applications, Hyper-threading can actually lead to a degradation in application performance (we have seen 5+ %).
For software that is not Hyper-threading aware and is licensed based on the number of CPU cores.

Older operating systems may falsely interpret the Hyper-threading CPU as 2 physical CPUs. Even with a modern operating environment that properly recognizes it as 2 logical CPUs, applications need to be updated to understand the concept of logical processors. Otherwise applications that are licensed based on the number of physical CPUs may improperly assume that the operator has violated the license. In some cases the software may cease to function.

Which major x86 OSs make use of Hyper-threading today

Solaris 8 and above
Red Hat Linux 9 and above
Red Hat Enterprise Linux 3 and above
SuSE Linux 8.2 and above
SuSE Enterprise Linux
Microsoft Windows 2003 Server (all versions)
Microsoft Windows XP (all versions except non-patched Home Edition)

Previously Published As 71205

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